The first mass-selective vibrational spectra have been recorded for Na(NH3)(n) clusters. Infrared spectra have been obtained for n = 3-8 in the N-H stretching region. The spectroscopic work has been supported by ab initio calculations carried out at both the DFT(B3LYP) and MP2 levels, using a 6-311++G(d,p) basis set. The calculations reveal that the lowest energy isomer for n <= 6 consists of a single solvation shell for the NH3 molecules, although in the case of n = 5 and 6 there are two-shell isomers that are reasonably close in energy to the single-shell global potential energy minimum. The infrared spectra concur with the ab initio predictions, showing similar spectra for the n = 3-6 clusters but a marked change for n = 7 and 8. The change in spectroscopic features for n >= 7 is indicative of molecules entering a second solvation shell, i.e., the inner solvation shell around the sodium atom can accommodate a maximum of six NH3 molecules.